Film plasticized with plasticizer having low vapour pressure

ABSTRACT

A central aspect of the present invention relates to a film of biodegradable material plasticized with a plasticizer of low vapour pressure, the film comprising on one or both surfaces a coating of glass or metal. Hereby a dilemma is solved: Glass and metal can only be vapour-deposited on polymers that do not contain plasticizers, as the plasticizer evaporates during the vacuum process. By selecting plasticizers with a low vapour pressure, the problems due to evaporation are solved.

FIELD OF THE INVENTION

The present invention relates to a film suitable for use as an ostomybag.

BACKGROUND

In connection with surgery for a number of diseases in thegastrointestinal tract a consequence is, in many cases, that the colon,the ileum or the urethra has been exposed surgically and the patient isleft with an abdominal stoma and the effluents or waste products of thebody, which are conveyed through these organs, are discharged throughthe artificial orifice or opening and are collected in a collection bag,which is usually adhered to the skin by means of an adhesive wafer orplate having an inlet opening for accommodating the stoma. Also, inconnection with a fistula, the patient will have to rely on an applianceto collect the bodily material emerging from such opening.

When replacing the ostomy bag, it would be advantageous for anostomy-operated patient if the used ostomy bag could be w.c. disposableinstead of having to go with the day refuse with odour problems as aconsequence. However, in order to make such flushing of the used bagenvironmentally friendly it is required that the bag is biodegradable.

EPO703762 describes a so-called bag-in-bag solution. Here, the outer bagis similar to a conventional ostomy bag with charcoal filter. This outerbag provides the barrier towards odour. The inner bag, which is theflushable one, is biodegradable and or/water soluble. The two bags areseparated before the inner bag is flushed out in the w.c.

GB2083762 describes a film made of PVOH coated with PVDC, vinylchloride-vinylidene chloride-copolymer, atactic polypropylene,nitrocellulose, waxes, greases, silicones, or pressure-sensitiveadhesives. The principle in a multi-layer laminate is that abiodegradable and/or water-soluble layer gives the main part of themechanical strength, and a mechanical weak layer gives the main part ofthe barrier properties.

In the course of time several experiments have been made to prepareflushable ostomy bags, but the preparation of a foil that is bothbiodegradable and at the same time has the sufficient barrier towardsfaeces odour has not succeeded until now.

SUMMARY OF THE INVENTION

The present invention discloses the construction of a biodegradable filmthat has a barrier towards faeces odour and with no cracking sounds.This is obtained by using a particular low vapour pressure plasticizerfor the film material, followed by routine vacuum deposition of a glassor metal layer.

DETAILED DISCLOSURE

A central aspect of the present invention relates to a film ofbiodegradable material plasticized with a polymeric plasticizer oranother plasticizer of low vapour pressure, the film comprising on oneor both surfaces a coating of glass or metal.

This film meets the following requirements:

-   -   1) It is biodegradable, i.e. 90 percentage of the weight of the        film is degraded after six months (as determined by ISO 14852);    -   2) It is impervious to water and faeces odour for at least 10        hours;    -   3) It is not more stiff or more crackling than films presently        used for ostomy bags.

In preferred embodiments, the film also is heat-sealable andtransparent.

Hereby a dilemma in the art is solved: Glass and metal can only bevapour-deposited on polymers that do not contain plasticizers, as theplasticizer evaporates during the vacuum process. By selectingplasticizers with a low vapour pressure, the problems due to evaporationare solved. The present invention thus provides an ostomy bag comprisinga film of biodegradable material plasticized with a plasticizer having alow vapour pressure, the film comprising on at least one surface acoating of glass or metal

It is preferred that the vapour pressure of the plasticizer is below10⁻⁴ mm Hg at 25° C. The vapour pressure depends on the pressure usedduring the glass deposition process. In one embodiment the plasticizeris a plasticizer with a vapour pressure below 10⁻⁷ mm Hg at 25° C.

The table shows the approximate vapour pressure for some commonmonomeric plasticizers. It is seen that it is also possible to choose acommon plasticizer with a low vapour pressure. F.x. Benzoflex 50supplied from Velsicol Chemical, which is compatible with PLA and has avapor pressure of 2,29×10⁻⁷ mmHg at 25° C.

Vapor pressure range (mm Hg at 25° C.) Chemical name 10⁻³ Dimethylphthalate, Diethyl phthalate, Diisobuthyl phthalate 10⁻⁴ Diallylphthalate 10⁻⁵ Di-n-butyl phthalate, Dihexyl phthalate 10⁻⁶ Butyl benzylphthalate, Diisooctyl phthalate, Dibutyl sebacate, Di-n-octyl phthalate,Acetyl tributyl citrate, Di-(2-ethylhexyl) azelate, Di-(2-ethylhexyl)sabacate 10⁻⁷ Di-(2-ethylhexyl) adipate, Di-n-octyl adipate, Tricresylphosphate, Diisononyl phthalate, Diisodecyl phthalate, Dinonyl phthalate10⁻⁸ Di-(2-ethylhexyl) phthalate 10⁻⁹ Diundecyl phthalate  10⁻¹⁰  10⁻¹¹Tri-(2-ethylhexyl) trimellitate, Ditridecyl phthalate George Wypych,Handbook of Plasticizers, p. 605, ChemTec Publishing, Toronto 2004.

In one embodiment the plasticizer is a polymer itself, for example apolyester plasticizer. In another embodiment, the plasticizer is amonomeric plasticizer.

The amount of plasticizer used is 5-50%, such as 10-30% depending on howsoft the material (the film) should be.

Applying the plastizicer to the film material is well known to theskilled person. In one method, the plasticizer is compounded into thepolymer in a molten state by means of an extruder or a mixer at elevatedtemperature. Alternatively the polymer is dissolved and mixed withplasticizer. Subsequently a film can be casted from the mixture.

The purpose of the coating of the at least one side of the film is tomake the film odour, water an moisture impermeable. Thus, the coating isa continuous layer of a glass or metal. It is well known that a layer ofSiOx or aluminum improves the barrier properties of a PET film (see FIG.1 from: Barrier Technologies, AIMCAL Fall Technical Conference, Dr. B.M. Henry, University of Oxford, 2005). Similar barrier improvements areseen by coating a biodegradable film with SiOx or aluminum.

Vacuum deposition of glass or aluminum to the film material is wellknown to the skilled person. An example of such procedure is describedin “Barrier properties of SiOx-coated polymers: multi-layer modellingand effects of mechanical folding”, M. S. Hedenqvist, Surface andCoatings Technology 172 (2003) 7-12.

Vacuum deposition, or co-extruding of the film material with otherbarrier coatings is also conceivable. That includes other metal oxidesor DLC (diamond like carbon) and organic polymeric surfaces optionallycontaining Si, Cl or F.

In one aspect of the invention the biodegradable material is degraded90% (of weight) after six months. It is, however, preferred that thebiodegradable material is degraded 100% after six months, allowing for10% of the weight of the film to be non-degradable material (e.g. thecoating of glass or metal). In a preferred embodiment, the biodegradablematerial is selected among biodegradable polyesters in general.Particularly preferred is the biodegradable material selected from thegroup consisting of PVOH (polyvinyl alcohol), Starch, PLA (polylaticacid), PHB (polyhydroxybutyrate), and Polycaprolactone. Examples of suchfilms are Mater-Bi, Eco-flex and PVOH.

In the present invention, a “film” is understood as a thin, planar sheetwith a thickness of about 10-100 micrometer. Typically, the dimensionsof the film for use as an ostomy bag (height×width) are in the range of126×200mm.

This solution is advantageous, as you do not need to separate bagsbefore flushing the inner bag and keeping the (somewhat soiled) outerbag.

The film can also be used in other contexts, wherebiodegradability/solubility shall be combined with a high barrier, forinstance for urine bags, but also in completely other connections wherea product is to be sealed, for instance for packaging of foodstuffs orwhere a controlled release is desired, i.e. the packagingdegrades/dissolves, whereby the contents is released.

EXAMPLES Example 1 Plasticizing PLA

A plasticized PLA film is made by using a twin-screw extruder(ThermoPrism Eurolab) with a 16 mm screw diameter and 30 L/D. Theprocessing temperature is set at 125-180° C. from feed inlet to the die.The extruder is equipped with a film sheet die and a film take-off unit.

PLA pellets (Biomer L9000) are gravimetrically fed and the plasticizer(Benzoflex 50 [50:50 diethylene glycol dibenzoate : dipropylene glycoldibenzoate]) volumetrically added simultaneously further down theextruder barrel, where the referred PLA pellets are melted. This resultsin an extrusion of a 50 μm thick and 10 cm wide film. The composition ofthe film is 80% PLA and 20% Benzoflex.

Example 2 Plasma Deposition of SiOx

A 50 μm plasticized film sample (80% PLA, 20% Benzoflex) is coated withSiOx by the use of plasma deposition. The plasticized film sample isplaced in a reactor and a mixture of hexamethyidisiloxane (HMDSO) andoxygen is added in the reactor producing the SiOx compound, which coatsthe film sample. This deposition is performed with the parametersettings shown in the table below:

Type of Process gas/ Power Flow rate Pressure Deposition Frequencyplasma monomer (W) (sccm) (mtorr) time (min.) (kHz) SiOx HMDSO + O₂ 1502.5:25 75 1 140 1:10

Example 3 Crackling of Bags

It is important to have a soft film, as cracking of the film isunfortunate. In order to determine the crackling of bags, three blindedpeople were asked to determine the cracling on a scale from 1=nocrackling to 5=very crackling.

The table below shows three people's evaluation of the crackling ofthirteen different films. Films E and F are the type of films that areused for conventional ostomy bags. The films E and F are the goldenstandard for how little crackling is acceptable.

Film I is a non-plasticized biodegradable film. Films J, K, L and M areplasticized biodegradable films. Film I is very crackling, whereas theplasticized films are less crackling. All these films (A-M) are withoutglass barrier layer, and the glass layer (N) is not expected to addconsiderably to the crackling.

Films G and H are water-soluble PVOH films. Film H is embossed, i.e. thesurface has a pattern structure which seems to lower the crackling.

Films A, B, C and D are common films.

Person Person Person Type I II III Average STDEV A: PET 50my 5 5 5 5.00.0 B: LDPE 40my 3 4 3 3.3 0.6 C: EMA 70my 1 2 1 1.3 0.6 D: PU 60my 1 31 1.7 1.2 E: Saranex 630 80my current ostomy bag 2 3 3 2.7 0.6 F:Saranex 114 60my current ostomy bag 4 4 3 3.7 0.6 G: PVOH 80my 4 5 4 4.30.6 H: PVOH (embossed) (80my) 3 3 2 2.7 0.6 I: PLA 20my Non plasticized5 5 5 5.0 0.0 biodegradable film J: PLA + 20% Benzoflex plasticizedbiodegradable 4 4 4 4.0 0.0 50my film K: Mater-Bi 90my plasticizedbiodegradable 4 4 4 4.0 0.0 film L: Mater-Bi 20my plasticizedbiodegradable 3 2 1 2.0 1.0 film M: Ecoflex 40my plasticizedbiodegradable 2 4 2 2.7 1.2 film N: PLA + 20% plasticized coated 4 4 4 40 Benzoflex 50my, coated biodegradable film with SiOx

It can be observed from the above table that the plasticized PLA film(J) is about as crackling as a typical film for ostomy bags (Saranex114, F). It can also be observed that a SiOx-coating is not expected toincrease the crackling noticeably (N).

Example 4 Odour of Bags

To determine the odour coming through the bag, we conducted thefollowing test. Bags of each material were made out of two pieces offilm (120×120 mm). The films are heat sealed at three sides. The lastside is welded after adding 1 ml of a 0.2% aqueous skatol solution. Thebags are placed in separate closed glass jars and kept at 32° C. Threeblinded people at three different time points evaluate the smell.

The odour scale was 0=no smell, 3=strong smell

1.5 h 4 h 24 h L: Mater-Bi 20my plasticized biodegradable film 1 2 3Mater-Bi 80my 0 2 3 Ecoflex 1 3 3 E: Saranex 630 current ostomy bag 0 00 F: Saranex current ostomy bag 0 0 0 B: LDPE 40my 2 3 3 G: PVOH 2 3 3

It is seen that the PVDC containing Saranex films are much better thananything else and set the goal for the odour barrier. Neither a commonnon-biodegradable film like LDPE nor any biodegradable films provide asufficient barrier towards ostomy gases. It is expected that theplasticized biodegradable films with deposited glass layer provide asufficient barrier towards ostomy gases, as determined by this skatoltest.

1: Film of biodegradable material plasticized with a plasticizer havinga low vapour pressure, the film comprising on at least one surface acoating of glass or metal. 2: Film according to claim 1, wherein thevapour pressure of the plasticizer is below 10⁻¹ mm Hg at 25° C. 3: Filmaccording to claim 1, wherein the vapour pressure of the plasticizer isbelow 10⁻⁴ mm Hg at 25° C. 4: Film according to claim 1, wherein thevapour pressure of the plasticizer is below 10⁻⁷ mm Hg at 25° C. 5: Filmaccording to claim 1, wherein the plasticizer is a polymericplasticizer. 6: Film according to claim 5, wherein the polymericplasticizer is a polymeric polyester plasticizer. 7: Film according toclaim 1, wherein the plasticizer is a monomeric plasticizer with avapour pressure below 10⁻⁴ mm Hg at 25° C. 8: Film according to claim 1,wherein the plasticizer is a monomeric plasticizer with a vapourpressure below 10⁻⁷ mm Hg at 25° C. 9: Film according to claim 1,wherein the film comprises a coating of glass or metal on one surface.10: Film according to claim 1, wherein the film comprises a coating ofglass or metal on both surfaces. 11: Film according to claim 1, whereinthe biodegradable material is degraded 90% (of weight) after six months.12: Film according to claim 1, wherein the biodegradable material isselected from the group consisting of PVOH (polyvinyl alcohol), Starch,PLA (polylatic acid), PHB (polyhydroxybutyrate), and Polycaprolactone.13: Film according to claim 1, wherein the film has a thickness of 10 to100 micrometer.